1. Field of the Invention
The present invention relates to a light emitting device for letting an LED (light-emitting diode) emit light and a light receiving and emitting driving circuit.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. Hei 7-134556 (see mainly paragraphs of the DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS and drawings) discloses a two-dimensional residual image display unit. This two-dimensional residual image display unit controls light emission of a plurality of LEDs using a residual image data stored in a memory. When the two-dimensional residual image display unit is swung while held in someone's hand, a residual image based on the residual image data stored in advance is formed.
Japanese Patent Application Laid-Open No. 2001-197253 (see mainly paragraphs of the DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS, FIG. 1 and FIG. 2) discloses an information output device and a line sensor device. These devices include a plurality of LEDs, a plurality of light receiving circuits and light emitting and receiving circuits connected to respective LEDs, a multiplexer connected to the plurality of light receiving circuits and light emitting and receiving circuits, and a CPU outputting a control signal to the multiplexer, the plurality of light receiving circuits and light emitting and receiving circuits.
In the devices disclosed in the 2nd Japanese Patent Application, the light emitting and receiving circuit lets the LED emit light, and a received light amount of LED adjacent to the light emitting LED is read based on an output signal from the light receiving circuit or the other light emitting and receiving circuit. In the devices disclosed in the 2nd Japanese Patent Application, when the light emitting LED performs reading, the other light emitting and receiving circuit lets the other LED emit light.
Thus, conventionally, a two-dimensional residual image display device using LEDs and a device using LEDs as a light receiving element have been proposed.
The present inventor conceives to adopt these arts using LEDs as light receiving elements to a portable light emitting device and conceives that the device forms a residual image which was read by itself. The portable light emitting device enables to form a image which is not memorized in itself beforehand The portable light emitting device can store a plurality of image data but the number of the images is not so manybut several at most. There is no limitation in the number of the formable images of the adopted portable light emitting device.
However, there is another problems to adopt these arts using LEDs as light the portable light emitting device is provided with a lot of LEDs. All of the LEDs which are used to form a read image are required to be connected to a light receiving circuit or to a light receiving and emitting circuit respectively. The portable light emitting device is thereby increased in size. It is difficult to be swung while held in someone's hand.
Incidentally, even when applying the device using the LEDs as a light receiving element to the light emitting device having the plurality of LEDs except the portable light emitting device, the light emitting device is also increased in size.